German patent specification DE 10 2008 020 41 B3 relates to a feeding device for in-line screw machines, in particular to avoid bridging in the medium to be conveyed. Generating unsymmetrical shear forces on opposing sides of the conveyor screw avoids the formation of textures in the medium that lead to bridging. This is realized by two disk wheels, which are driven by the conveyor screw. In addition, the disk wheels are equipped with strips that recirculate and/or loosen any material that might have dammed up in the feeding device.
Design patent DE 298 08 800 U1 discloses a feeding device for screw conveyors. In this configuration, the screw conveyor simultaneously serves as the drive for the catch element of the feeding device. The five depicted catch elements join together two wheels, the bearings of which are arranged on the same rotational axis. Since the catch elements engage into the screw flights, the feeding device rotates as soon as the conveyor screw operates. The advantage to this arrangement is that it requires no additional drive for the feeding device. However, there is little avoidance of the bridging expected to arise when conveying heavy conveying media.
The German translation DE 35 86 241 T2 of European patent specification EP 0 185 541 B1 describes a screw conveyor, in which two parallel, spaced apart conveyor screws rotate in a housing. To improve the way the product to be conveyed gets into or between the screw flights, draw-in rollers with wings are provided, arranged either one perpendicular or two parallel to the conveyor screws. The draw-in rollers with their movable wings that engage into the product are situated above the conveyor screws, and to the side of the latter in the dual configuration, and made to rotate independently of the conveyor screws of separate drives.